1. Field of the Invention
The present invention relates to recording apparatuses for making a recording on recording materials using recording heads, and more specifically, relates to a recording apparatus including a conveying roller disposed upstream of a recording head and an eject roller disposed downstream of the recording head, and capable of recording on recording materials using the recording head even after the trailing ends of the recording materials pass through the conveying roller.
2. Description of the Related Art
Among conventional recording apparatuses, some include a recording head for making a recording on recording materials while scanning in a main scanning direction, a conveying roller disposed upstream of the recording head for conveying the recording materials, and an eject roller disposed downstream of the recording head for conveying the recording materials. The conveying roller and the eject roller are driven by the torque of a DC motor transmitted via gears or timing belts. Moreover, a code wheel having marks with a pitch of about 150 to 300 lpi used for detecting the amount of rotation of the conveying roller is disposed on the shaft of the conveying roller or on a driving line adjacent to the conveying roller, and the amount of rotation of the conveying roller is controlled on the basis of signals output from an encoder sensor that reads the marks on the code wheel.
In such recording apparatuses, actual conveying amounts sometimes differ from a target value due to factors such as variations in outer diameters, deviations, and frictional coefficients of the conveying roller and the eject roller, conveyance load exerted on the recording material, stiffness of the recording material, and moisture in the recording material. When the actual conveying amount is larger than the target value, white streaks may be generated in images. In contrast, when the actual conveying amount is smaller than the target value, black streaks may be generated in images. There is a need to solve this problem with the recent development toward photorealistic printing.
In an attempt to solve this problem, the dimensions of parts of the conveying roller and the eject roller have been held to closer tolerances, or the conveying path of the recording materials has been changed so as to reduce the conveyance load exerted on the recording materials. However, these countermeasures cannot solve the problem completely.
In order to correct variations in the conveying amount in each apparatus, Japanese Patent Laid-Open No. 2004-175092 describes a technique for correcting the conveying amount of printing media on the basis of correction patterns printed on a printing sheet. Moreover, Japanese Patent Laid-Open No. 2004-175092 describes another technique for coping with errors in the conveying amount that differs in accordance with printing modes by correcting the conveying amount for each conveying speed or each print resolution, either of which differs in accordance with print quality. Furthermore, Japanese Patent Laid-Open No. 2004-175092 describes yet another technique for correcting the conveying amount in an area of a printing sheet conveyed by the conveying roller and the eject roller and the conveying amount in an area of the printing sheet conveyed by the eject roller after the trailing end of the printing sheet is separated from the conveying roller.
The techniques described in Japanese Patent Laid-Open No. 2004-175092 may correct the conveying amounts while the printing sheet is nipped by a conveying roller unit and an eject roller unit and while the printing sheet is nipped by only the eject roller unit. However, the techniques described in Japanese Patent Laid-Open No. 2004-175092 are not designed to correct the conveying amount when the trailing end of the printing sheet is separated from the conveying roller unit. The conveying amount of the printing sheet when the trailing end is separated from the conveying roller unit can be corrected on the basis of a correction pattern printed when the trailing end is separated from the conveying roller unit. However, it is necessary to print on a plurality of printing sheets while the correction value is changed since the trailing end of one printing sheet is separated from the conveying roller unit only one time. Thus, it is difficult to conduct such correction in practice.